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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 1Dr. Eulitz 02.06.1999- Rev 1 This presentation gives a short explanation of harmonics and reactive power consumption of 6-pulse converters A rectifier with a 6-pulse thyristor bridge is a typical non-linear load For the explanation we use an ideal converter model which is connected to an infinite inductive load. The resulting direct current is ideal smoothed

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 8Dr. Eulitz 02.06.1999- Rev 1 Distortive reactive power Harmonics do not participate in transmission of active power They generate harmonic reactive power Distortive reactive power

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 10Dr. Eulitz 02.06.1999- Rev 1 Influence of firing angle Changes of the firing angle cause also a phase shift of the harmonics. (Related to the fundamental wave of the voltage) The active power consumption of thyristor rectifiers also depends on the firing angle

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 14Dr. Eulitz 02.06.1999- Rev 1 Estimation of DC-drive‘s reactive power consumption Converter’s apparent power at net-connection S L U d, I d motor connection of converter Active power consumption at net- and motor-connection are identically Motor-voltage U d can be calculated from motor speed, Motor-current I d from motor-torque (Attention in field weakening mode!)

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 15Dr. Eulitz 02.06.1999- Rev 1 Estimation of bus bar-drive‘s reactive power consumption The intermediate DC-voltage circuit can only transmit active power! The reactive power for the induction machines is stored in the backup capacitors. This means for the active power at the net connected converter: for diode supply unit for thyristor supply unit (mainly caused by the safety margin)

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 16Dr. Eulitz 02.06.1999- Rev 1 This presentation does not explain: Effects of commutation  commutating reactive power Influence of ripple Statistic effects with many installed drives Influence of rectangle currents‘s edge steepness More information on harmonics, reactive power and reactions on system in the Power NetAnalysis engineer’s training course